AN IMPROVED TELEPHONE SET 267 



play. At this point, however, the coil spring mechanism is approaching dead 

 center, and very little buildup in operating force is encountered. This as- 

 sures correct seating of the lightweight handset on the mounting. 



The switch is base mounted with the contact springs vertical to make 

 efficient use of the space available. A plastic cover is provided to protect the 

 spring assembly. Simplicity of design has been maintained in order to facili- 

 tate manufacture. Only two screws are required in the complete assembly, 

 most of the parts being held together by snap-on arrangements. 



Set Assembly 



In the design of the new telephone set, full advantage was taken of the 

 fact that all the components were being developed simultaneously. Thus, 

 for instance, the ringer and network have been designed to nest together 

 to save space. The switch mounting has been designed to accommodate a 

 flexible support for mounting one end of the ringer. The switch has been 

 laid out to require as Httle space as possible at the base, where space is at a 

 premium, and spreads out at the top where more space is available. 



Means are provided for the production of other varieties of set from the 

 basic set assembly. The dial bracket is punched to permit the addition of a 

 ten-terminal block for sets to be used in key systems. Holes are provided 

 in the base for mounting a turn button key and a cold cathode tube for 

 selective ringing. The switch bracket is punched to accept the mounting 

 lug of an exclusion key. The housing is molded with a welled section which 

 is easily drilled out to support the stem of a turn button key. These features 

 permit the manufacture, on a single assembly Hne, of a variety of sets start- 

 ing with the basic set, which may be modified at special stations on the 

 line or by running the various types alternately on the one Hne. 



The basic set has the following components: the handset and cords, the 

 ringer, network, switch, dial and equalizer. The internal wiring is done by 

 means of eleven leads from the switch assembly, four leads from the dial, 

 and four leads from the ringer. The housing merely serves as a cover and is 

 assembled at the final position on the line. 



The network, equalizer and switch are permanently attached to the base. 

 Dial, ringer, handset and cords may be replaced by disconnecting spade 

 tips from readily accessible screw terminals. Wiring modifications for vari- 

 ous types of service are accomplished in the field by rearranging spade tips. 



Field Trials 



As invariably is done with developments of major importance, the new 

 set designs have been given a comprehensive service trial. This is essential 

 in verifying laboratory tests and engineering assumptions. The locations for 

 such trials were chosen to represent the range of service and climatic 



